The present invention relates to a new and improved construction of water decomposition apparatus for producing detonating gas or oxyhydrogen gas. U.S. Pat. No. 3 957 618 granted to the present applicant on May 18, 1976 for WATER DECOMPOSITION APPARATUS FOR PRODUCING DETONATING GAS describes an apparatus including a concentric array of open-topped electrolytic cells through which electrolyte passes in succession. The cells are of progessively different heights and the flow of electrolyte is produced by successive overflowing from each into the next.